The invention relates to ram-type blowout preventers used in well operations, such as in the recovery of hydrocarbons, for well control including preventing a well blowout. More particularly, the present invention pertains to the construction and operation of sealing devices included in the blowout preventers, and finds particular application in the operation and testing of subsea blowout preventers and other apparatus in a blowout preventer stack.
Blowout preventers are typically included in the assembly at a wellhead when drilling or completing a well to close off the well to prevent a blowout. Such a blowout might occur, for example, when the well suddenly intersects a pocket of fluid under high pressure, which then blows up the well bore. A blowout preventer seals the well against the fluid pressure from below. A blowout preventer can also be used to seal off the well around a well pipe in normal drilling operations involving positive downhole pressure. In practice, multiple blowout preventers are arrayed in a vertical stack, which is positioned over the well, with the well piping extending up through the center of the blowout preventer stack.
FIGS. 1 and 2 provide two views of an underwater blowout preventer stack shown generally at 10. Various hydraulic lines, framework and control apparatus for operating the blowout preventer stack 10 are not shown for purposes of clarity. The stack 10 includes four ram-type blowout preventers 12, 14, 16 and 18. An annular blowout preventer 20, a connector 22, a second annular blowout preventer 24 and a flex joint 26 are arrayed above the ram-type blowout preventers 12-18. A riser adapter 28 is positioned at the top of the stack 10 for connection to a marine riser above (not shown). A wellhead connector 30 is located at the bottom of the stack 10 for connection to a wellhead below (not shown). In general, the number and kind of blowout preventers in a stack, as well as the order in which they are arrayed in the stack, may vary.
A ram-type blowout preventer includes a pair of linear drive devices, or linear actuators, located on opposite sides of a central housing to provide movement along a straight line, perpendicular to the vertical, toward and away from the housing. For example, a ram-type blowout preventer such as shown at 12 provides a pair of piston and cylinder assemblies 32 and 34 with the cylinders fixed on opposite sides of a central housing 36 positioned over the well so that the pistons are movable along a line perpendicular to the vertical, that is, perpendicular to the well bore at the surface of the well. As shown, the bottom two blowout preventers 12 and 14 have a common, extended central housing 36. A central vertical bore through the housing 36 is aligned with the well bore so that well pipe extending from the well passes upwardly through the housing along its central bore. The pistons are hydraulically operated to simultaneously move toward each other, or away from each other. Each piston carries a ram at the piston end toward the well, so that the two rams meet in a closed configuration at the housing central bore when the pistons are driven together, and are pulled apart by the pistons to an open configuration. The central vertical bores through housings of the ram-type blowout preventers 12-18 form part of a central vertical passageway extending from the wellhead and the well bore below, up through all of the elements in the blowout preventer stack 10 and on through the marine riser.
A cavity is provided within the central housing for each ram-type blowout preventer 12-18, that is, for each pair of piston and cylinder combinations 32/34. Each cavity intersects the vertical bore of the housing 36 and extends radially outwardly toward the piston and cylinder structures 32 and 34 in two guideways 38 and 40, with each guideway interposed between the central housing and a corresponding piston and cylinder assembly. The ram carried by a piston resides and moves within the corresponding guideway.
The rams in a multiple blowout preventer stack may operate in different ways in closing off the well. Pipe rams seal around a tubular pipe extending from the well, closing off the annulus between the well pipe and the well bore surface. Blind rams seal across the well with no pipe at the location of the blind ram. Shear, or cutting, rams shear the well pipe, but do not seal off the annulus around the pipe. Blind shear rams shear the well pipe and close and seal the well. A blowout preventer with blind shear rams is typically at the top of a ram-type blowout preventer stack, with various pipe rams in blowout preventers located below. In a typical application, the top ram-type blowout preventer 18 would be fitted with blind shear rams, and the lower preventers 12-16 would contain pipe rams.
FIG. 3 shows a matched pair of pipe rams generally at 42 and 44, and is used herein to illustrate various features of rams. To the extent that the rams 42 and 44 are alike, the same number label is used to identify their like parts and features. Each of the rams 42 and 44 includes a ram body 46 having a groove 48 in its front, or leading, end. A packer 50 is carried in the groove 48. A groove 52 extends across the top surface of the ram body 46. A top seal 54 is received within the top groove 52 such that the ends of the top seal extend to the ends of the packer 50. A T-slot 56 is cut into the back of each ram body 46 to receive a button at the end of a linear drive device (not shown), such as are included in the piston and cylinder assemblies 32 and 34 (FIGS. 1 and 2), used to operate the rams 42 and 44.
The ram bodies 46 are generally curved, oblong cylinders as shown. The guideways (not shown) are also curved, oblong cylindrical inner surfaces that receive the rams 42 and 44, and along which the rams are driven by the corresponding pistons. In general, blowout preventer ram bodies and corresponding guideways may also have other cross-sectional shapes, such as circular or rectangular. When the rams 42 and 44 are driven together, they meet at the well pipe (not shown) within the central vertical passageway within the blowout preventer stack 10. The pipe ram packers 50 feature a vertical, cylindrical groove 58 that receives the well pipe, and the front ends of the ram bodies 46 are cut to fit together with each other. Thus, in the closed configuration, the pipe rams 42 and 46 fit together and around the well pipe to enclose the well pipe in annular sealing engagement. To complete the sealing of the well with the rams 42 and 44 in the closed configuration, the rams must be sealed to their respective guideways against well fluid under pressure from moving around the rams and up into the housing above the level of the ram packers. This sealing is provided by the top seals 54 that engage the interior guideway surfaces in a sliding seal. Consequently, the combination of the top seal 54 and the packer 50 of a ram 42 or 44 completes the seal between the well pipe and the corresponding guideway, and the pair of rams 42 and 44 in the closed configuration completes the sealing of the annulus of the well bore surrounding the well pipe.
Each ram 42 and 44 is provided with a pressure equalization path in the form of a groove, or mud slot, 60 machined longitudinally into the bottom surface of the ram to communicate fluid pressure between the vertical bore of the central housing below the ram packer 50 and the respective guideway behind the ram seals. Thus, each ram 42 and 44 may be driven back and forth along its guideway without having to work against fluid pressure differentials between the area behind the ram and the central vertical passageway through the stack 10 below the packers 50.
Each of the ram-type blowout preventers 12-18 has an access port 62 (FIGS. 1 and 2) toward the bottom of each side of the corresponding central housing 36. The ports 62 of each blowout preventer 12-18 are positioned to communicate with the central vertical passageway within the stack 10 at a location below where the ram packers of these blowout preventers would cooperate to form a seal. A choke line 64 extends along the side of the stack 10 and is connected to access ports 62 of the blowout preventers 12 and 16, and controlled there by valves 66. A choke line can be used to bleed off high fluid pressure from downhole by tapping through an access port 62 at a closed and sealed blowout preventer. A kill line 68 extends along the opposite side of the stack 10 and is connected to access ports 62 of the remaining ram-type blowout preventers 14 and 18, and controlled there by valves 70. A kill line can be used to feed high-pressure fluid or high-density mud into the well through an access port 62 at a closed and sealed blowout preventer.
In practice, blowout preventers are periodically tested for their ability to seal against downhole pressures. This is particularly true in cases of underwater installations. A test tool is lowered through the blowout preventer stack on a pipe, and anchored below the lowest blowout preventer in the stack. The test tool is actuated to seal the well at that point. A blowout preventer to be tested is moved to its close, or sealed configuration. Then, fluid pressure is communicated into the annular region surrounding the pipe above the test tool and below the blowout preventer under investigation by means of the choke line 64 or the kill line 68 to carry out the testing. A major disadvantage of this testing operation is that it requires that the drill string, or whatever tubing is being used in the well, must be pulled from the well so that the test tool may be installed in the well. After testing, the test tool is removed and the original tubing is then run back into the well. Such tripping is time consuming and expensive, particularly in the case of a deep well or of a well in deep water.
An alternative to pulling the well pipe to test the rams is provided by adding another ram-type blowout preventer at the bottom of the blowout preventer stack. The rams of the added blowout preventer are installed inverted, so that their sliding seals that contact the guideways are on the bottom of the rams rather than on the top of the rams, as illustrated in FIG. 3. Also, the pressure equalization grooves 60 are on the top of the inverted rams to allow fluid communication between the areas behind the two rams and the central passageway above the inverted rams and below the blowout preventer being tested. These inverted rams are closed to seal about the well pipe already in place in the well, against fluid pressure from above the rams. Then, fluid pressure is communicated into the annular region surrounding the well pipe above the inverted rams and below the blowout preventer under investigation by means of the choke line 64 or the kill line 68 to carry out the testing. The disadvantage of this test technique is that it requires an extra ram-type blowout preventer that is used only for testing other blowout preventers in the stack.
It is advantageous and desirable to provide a technique for testing blowout preventers and other apparatus in a stack that does not require pulling the well pipe, and a technique that does not add major apparatus to the blowout preventer stack that is only used for testing purposes. The present invention provides for such a technique.
The present invention provides a bidirectional sealing ram-type blowout preventer, and provides a blowout preventer stack including a bidirectional sealing ram-type blowout preventer.
A bidirectional sealing ram-type blowout preventer has bidirectional sealing rams having top seals, bottom seals, and packers at the front of each ram, a selectively operable first fluid communication system for equalizing fluid pressure between the back of each ram with fluid pressure below the ram packers, and a selectively operable second fluid communication system for equalizing fluid pressure between the back of each ram with fluid pressure above the ram packers.
A blowout preventer ram body according to the present invention has a receptacle at the front end for receiving a packer, a first groove across the top for receiving a top seal member and a second groove across the bottom for receiving a bottom seal member. A blowout preventer ram according to the present invention has a body, a receptacle at the front end of the body, a packer carried in the receptacle, a first groove across the top of the body, a top seal member carried in the first groove, a second groove across the bottom of the body, and a bottom seal member carried in the second groove.
According to the present invention, a ram-type blowout preventer fluid communication system has a selectively operable first fluid communication system for equalizing fluid pressure between the back of each ram of the blowout preventer with fluid pressure below the ram packers, and a selectively operable second fluid communication system for equalizing fluid pressure between the back of each ram of the blowout preventer with fluid pressure above the ram packers. A fluid communication system according to the present invention further includes first control apparatus for selectively opening and closing the first fluid communication system, and second control apparatus for selectively opening and closing the second fluid communication system. A control unit connected to the first control apparatus and to the second control apparatus may selectively operate the first and second control apparatus to open and close the first and second fluid communication systems, respectively. The first control apparatus may include at least one valve and the second control apparatus may include at least one valve.
The present invention provides a ram-type blowout preventer including a first ram connected to a first linear actuator and movable within a first guideway and including a ram body having a top, a bottom, a front end, a back end, a packer carried in a receptacle at the front end of the body, a top seal carried in a groove across the top of the body, a bottom seal carried in a groove across the bottom of the body, and being connected to the first linear actuator at the back end of the body, a second ram connected to a second linear actuator and movable within a second guideway and including a ram body having a top, a bottom, a front end, a back end, a packer carried in a receptacle at the front end of the body, a top seal carried in a groove across the top of the body, a bottom seal carried in a groove across the bottom of the body, and being connected to the second linear actuator at the back end of the body, a first fluid communication system between a central vertical passageway, through a central housing of the blowout preventer, below the level of the ram packers and locations in the first and second guideways behind the rams, first control apparatus for selectively opening and closing the first fluid communication system, a second fluid communication system between the central vertical passageway above the level of the ram packers and locations in the first and second guideways behind the rams, and second control apparatus for selectively opening and closing the second fluid communication system. The first linear actuator may comprise a piston and cylinder assembly and the second linear actuator may comprise a piston and cylinder assembly. The first fluid communication system may comprise fluid communication lines and at least one valve, and the second fluid communication system may comprise fluid communication lines and at least one valve. The first control apparatus may comprise at least one valve, and the second control apparatus may comprise at least one valve. The first and second control apparatus may be connected to a control unit by which the first and second control apparatus may be selectively operated to open and close the first and second fluid communication systems, respectively. The first fluid communication system may include fluid communication lines and may communicate with the central vertical passageway through at least one access port, the first control apparatus may include at least one valve, the second fluid communication system may include fluid communication lines and may communicate with the central vertical passageway through at least one access port, and the second control apparatus may include at least one valve. The second fluid communication system may communicate with the central vertical passageway through at least one access port that is located in the central housing of the blowout preventer, in an extension of the central housing above the blowout preventer, or in the central housing of a second, higher blowout preventer. All of the access ports by which the first and second fluid communication systems communicate with the central vertical passageway may be located in the central housing of the blowout preventer.
A method of operating a bidirectional sealing ram-type blowout preventer according to the present invention includes providing fluid communication between the area of fluid pressure against which the rams of the bidirectional sealing ram-type blowout preventer are to seal and the backs of the rams, and manipulating the rams between an open configuration and a closed, sealing configuration.
The present invention provides a method of operating a bidirectional sealing ram-type blowout preventer, including bidirectional sealing rams having top seals, bottom seals and front packers, operable by corresponding linear actuators for movement in corresponding guideways within a central housing to selectively seal the annulus around a pipe located within a central vertical passageway through the central housing, a selectively operable first fluid communication system between the central vertical passageway below the level of the ram packers and locations in the first and second guideways behind the rams, and a selectively operable second fluid communication system between the central vertical passageway above the level of the ram packers and locations in the first and second guideways behind the rams, including opening one and closing the other of the first and second fluid communication systems and operating the linear actuators to selectively move the rams in the corresponding guideways. The first and second fluid communication systems may be selectively operated to open and close using first control apparatus and second control apparatus, respectively, and the first and second control apparatus may be connected to a control unit by which the first and second control apparatus may be selectively operated. The first and second control apparatus may each include at least one valve. A method of operating the bidirectional sealing ram-type blowout preventer to apply fluid pressure above the bidirectional sealing ram-type blowout preventer includes closing the first fluid communication system with the second fluid communication system open, operating the linear actuators to move the rams to seal around a pipe in the central vertical passageway through the central housing, and applying fluid pressure within the vertical passageway above the packers of the rams of the bidirectional sealing ram-type blowout preventer. The present invention thus provides a method of testing a blowout preventer that is positioned above the bidirectional sealing ram-type blowout preventer. A method of operating the bidirectional sealing ram-type blowout preventer to seal against fluid pressure from below includes closing the second fluid communication system with the first fluid communication system open and operating the linear actuators to move the rams to seal around a pipe in the central vertical passageway through the central housing.
A method of pressure testing a blowout preventer in a blowout preventer stack, according to the present invention, includes providing a bidirectional sealing ram-type blowout preventer in the blowout preventer stack at a position below the blowout preventer to be tested, providing fluid communication between the area above the rams of the bidirectional sealing ram-type blowout preventer and below the blowout preventer to be tested, and the backs of the rams of the bidirectional sealing ram-type blowout preventer, closing the rams of the bidirectional sealing ram-type blowout preventer to sealing configuration, and, with the blowout preventer to be tested in its sealing configuration, applying fluid pressure between the rams of the bidirectional sealing ram-type blowout preventer and the blowout preventer to be tested.
The present invention provides a bidirectional sealing ram-type blowout preventer for sealing a well around a well pipe against fluid pressure from below for well control as well as sealing around a well pipe against fluid pressure from above for testing or pressure-activating other apparatus.